Question: A bag contains $10$ red balls, $5$ green balls, and $5$ blue balls. If a ball is randomly chosen, what is the probability that it is not red?
Solution: There are $10 + 5 + 5 = 20$ balls in the bag. There are $10$ red balls. That means $20 - 10 = 10$ are not red. The probability is $ \frac{10}{20} = \dfrac{1}{2}$.